Since definitive information on the transplancental transmission of influenza virus is lacking, a prospective investigation relating to this subject was initiated during a recent influenza epidemic in Hawaii. Appropriate specimens for laboratory confirmation of influenza were obtained from 15 pregnant women with an influenza-like illness. Infection with influenza virus (A/Hawaii/12/75(H3N2), similar to A/Victoria) was confirmed in 8. Thus far 2 of these women have delivered, and umbilical cord blood and placenta have been collected from each. Results of attempts to isolate virus from the placenta are pending. Tests for specific 1gM type influenza antibody in cord serum of each were negative.